It is an aim of chemical and biochemical analytics to develop detection methods with an increased sensitivity. Sensitive and highly specific analytical methods based on molecular interactions, for example of nucleic acids or proteins, have been developed in biochemical analytics, in particular. Such methods are used, for example, in process analytics, in molecular diagnostics, in molecular biological research, in clinical diagnostics, in food analysis and in environmental analytics.
Patent DE 100 583 94 C1 describes an electrochemical sensor that can be used for nucleic acid analytics. This sensor has electrodes to which there is applied a microarray arrangement of catcher oligonucleotides that can specifically bind nucleic acids to be detected. These nucleic acids to be detected can be marked or labeled with an enzyme that converts a substrate to an electrochemically detectable product. The current rise can be measured at the electrodes upon the emergence of the product. To raise the sensitivity of this measurement method, DE 100 583 94 C1 teaches the use of small volume detection spaces in order to amplify the local increase in concentration of the electrochemically detectable product, and thus to raise the sensitivity.
The sensitivity of such measurement methods is limited, on the one hand, by signal noise and, on the other hand, by the so called baseline drift that leads to a shift in the baseline in the course of time such that in the event of very small analyte concentrations it is not possible to make any reliable statement relating to a signal rise with reference to the baseline. This problem of baseline drift occurs not only in electrochemical measurement methods, but also with other detection methods, for example optical, magnetic and other methods. Baseline drift is conditioned by a multiplicity of causes, for example by temperature fluctuations, by interface effects at the interface from sensor to sample volume, in particular when use is made of measuring electrodes on the basis of polarization effects on measuring electrodes and sample solution, and by other effects.